1. Field of the Invention
The present invention relates to a data storage, and, in particular, to a data storage for which security can be effectively improved for stored information.
2. Description of the Related Art
Recently, leakage, robbery or such, of information to be protected, such as personal information, confidential information or such, has taken an attention as a social problem. As a result, countermeasures are demanded for various types of information processing apparatuses which handle such information to be protected.
Information to be protected may include, for example, information for identifying a person, such as a residence, a name or such, information applied for personal authentication such as fingerprint, password or such.
Such information to be protected is for example stored in a memory or a data storage in an information processing apparatus. In such a case, an appropriate countermeasure against data leakage should be taken for the memory or the data storage.
Memories or data storages used in information processing apparatuses may be roughly classified into two types, i.e., volatile memories and nonvolatile memories. The nonvolatile memories are configured such that, as well-known, stored data is held even without power supply.
Japanese Laid-open Patent Applications Nos. 5-88986, 2001-195307, 11-328036, 10-320293, 9-16477, 2002-73422 and 2001-202167 disclose related arts.